Either my iPad or my iTunes is demon-possessed (or it's a major case of operator-error

). I'm trying to replace some audio files I have on my iPad with new ones and I just can't get it to work. On iTunes it's showing that the old files are gone and replaced with the new files, but the old files are still, stubbornly, on the iPad, and the new ones are not there at all.
I hardly use iTunes (for this very aggravating reason

) and I've been at this more than an hour now. I'm ready to cry; please
I have an iPad 3, running iOS 7.1; my computer is Win7 64-bit, running iTunes 11.1.5.5. Any help would be much appreciated.